This section provides background information related to the present disclosure, which is not necessarily prior art.
Vehicle heating, ventilation, and air cooling (HVAC) systems include doors to direct airflow. A servo motor typically drives a linkage system that opens or closes one or more doors. The linkage system is often a gear-gear linkage or a pin-groove linkage.
In a gear linkage, a drive gear is directly connected to the servo motor. The drive gear is on a drive side of the linkage and is meshed with a driven gear on a driven side of the linkage. The driven gear rotates the door. Therefore, rotation of the drive gear by the servo motor drives the driven gear, which in turn moves the door to an open position, a closed position, or any desired position therebetween. Gear linkages are used for a variety of reasons, such as the following: the linkage is relatively compact because the drive and driven sides can be positioned close together; and the door can be accurately positioned because the drive and driven gears are continuously meshed with one another. In some instances, the servo motor may not be configured to immediately stop when the door contacts a mechanical stop at either the open or closed position. Because the gears are continuously meshed, continued operation of the motor after the door contacts a mechanical stop may subject the motor to undesirable stress and may damage the door.
In a pin-groove linkage, a drive arm on the drive side is rotated by the servo motor. The drive arm rotates a driven arm on the driven side, which either directly or indirectly moves the door to a desired position. The driven arm defines a track with a pin slidably seated therein. The drive arm is coupled to the pin. As the servo motor rotates the drive arm, the pin is moved through the track, which causes both the driven arm and the door coupled thereto to rotate. To accommodate both the drive and driven arms, the pin-groove linkage requires relatively large packaging, particularly as compared to a gear linkage.
In view of the shortcomings of both gear and pin-groove linkages, such as those described above for example, an improved linkage would be desirable.